Tan A=3/4 tan B=1/7. A dan B lancip maka cos (A+B) adalah...
subebe
Tan A = 3/4 sisi tinggi segitiga = 3 sisi mendatar = 4 sisi miring = √3² + 4² = √9 + 16 = √25 = 5 sin A = 3/5 cos A = 4/5 Tan B = 1/7 sisi Tinggi = 1 sisi mendatar = 7 sisi miring = √7² +1² = √49 + 1 = √50 = 5√2 sin B = 1/5√2 = √2/10 cos B = 7/5√2 = 7√2 / 10 cos (A+B) = cos A cos B - sin A sin B = 4/5 x 7√2/ 10 - 3/5 x √2/10 = 28√2/50 - 3√2/50 = 25√2/50 =√2/2 = 1/2 √2
sisi tinggi segitiga = 3
sisi mendatar = 4
sisi miring = √3² + 4² = √9 + 16 = √25 = 5
sin A = 3/5
cos A = 4/5
Tan B = 1/7
sisi Tinggi = 1
sisi mendatar = 7
sisi miring = √7² +1² = √49 + 1 = √50 = 5√2
sin B = 1/5√2 = √2/10
cos B = 7/5√2 = 7√2 / 10
cos (A+B) = cos A cos B - sin A sin B
= 4/5 x 7√2/ 10 - 3/5 x √2/10
= 28√2/50 - 3√2/50
= 25√2/50
=√2/2 = 1/2 √2